Diesel Particulate Filter (DPF)

Diesel particulate filters, also know as DPFs, are components designed to trap all solid particles that travel along with the exhaust gases in their honeycomb ceramic core. This filter, capture the particles and transform them periodically in a process called Regeneration that consist in increasing the temperature of the gases to a range between 500 and 620°C in order to reach the ignition point of those particles. Once ignited those particles are naturally transformed into carbon dioxide (CO2) thanks to a oxidation process. Regeneration process leaves the filter empty and ready to continue storing particles. This process takes place periodically and in normal driving circumstances the regeneration use to take place between 400 Km and 800 Km. The efficiency of the actual DPF systems trapping the solid particles of the exhaust gases is way above 98%. The internal ceramic core of these devices can be manufactured in two types of materials, silicone carbide (SiC) or cordierite (C) material depending on the vehicles driving needs.

Walker® diesel particulate filters (DPF) - Walker®DPF EVO S      

• The silicon carbide filter (SiC), is made of a dark grey color artificial mineral known for its very high hardness and abrasion resistance.
• Almost all original equipment manufacturers (with few exceptions) use silicone carbide filters to buildtheir DPF. 
• It has a melting point around 2650°C.
• Silicon carbide filters have also some weak points, due to its high coefficient of linear expansion (5.1mm/m-ºC (~25ºC through ±1000ºC) toward 1.7mm/m-ºC (~25ºC through ±1000ºC) of the cordierite), present packaging issues, to solve them small DPF SiC cores are made of single pieces, while larger DPF cores are made in segments, which are separated by aspecial cement so that heat expansion of  the core will be absorbed by the cement, and not the package.
• SiC cores are more expensive to produce than cordierite cores, however they are manufactures in similar sizes.                                                                                                                                                

Walker® diesel particulate filters (DPF) - Walker®DPF EVO C

• The cordierite is a ceramic material made of Aluminium magnesium silicate.
• (2MgO-2Al2O3-5SiO2) that is also used at catalytic converter monoliths.
• Diesel particulates filters look very similar to catalytic converter cores but with the unique difference that DPF cores have alternate channels plugged.
• Cordierite filters provide excellent filtration efficiency due to its porosity.
• Cordierite have also better thermal dilatation properties than the ones made or silicon carbide.This fact prevents thermal shock cracking from taking place when the DPF is used properly.
• Cordierite filters are cheaper to produce than the ones made of silicone carbide.

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